Polyphenylene sulfide filament yarns

ABSTRACT

A polyphenylene sulfide multifilament yarn having a filament linear density of 5 dtex to 30 dtex, an overall linear density of 500 dtex to 2500 dtex, a breaking tenacity in the range of 50 cN/tex to 80 cN/tex and an elongation at break of 8% to 16% for a yarn with a breaking tenacity in the range of 60 cN/tex to 80 cN/tex and an elongation at break of 16% to 30% for a yarn with a breaking tenacity in the range of 50 cN/tex to 60 cN/tex.

BACKGROUND

This is a Division of application Ser. No. 11/794,885 filed Apr. 9,2008, which in turn is a National Phase of PCT/EP2006/002338 filed Mar.14, 2006, which claims priority of European Patent Application No.05005914.6 filed Mar. 18, 2005. The disclosure of the prior applicationsis hereby incorporated by reference herein in their entirety.

The present invention relates to a process for producing a polyphenylenesulfide multifilament yarn, a polyphenylene sulfide multifilament yarnand the use of a polyphenylene sulfide multifilament yarn.

The term “filament” as used herein means fibers of practically endlesslength. Yarns consisting of a number of filaments are therefore calledfilament yarns.

Polyphenylene sulfide filaments are available as monofilament yarns,multifilament yarns or staple fibers. Polyphenylene sulfide filamentsare produced by a melt spinning process. They may be used attemperatures up to 190° C. without showing significant damage ordegradation. PPS filaments are flame resistant, self-extinguishing andmelt at temperatures of about 285° C.

DE 40 06 397 pertains to a process for production of mono- andmultifilaments as well as staple fibers made of polyphenylene sulfide.The process is a melt spun process. Below the spinneret air or inert gaswith a temperature between 50° C. and 150° C. is blown against thefilaments followed by multiple stage drawing to a total draw ratio of3.7 to 11.2. The process may yield a multifilament yarn with a tenacityof 76 cN/tex and elongation at break of 16%

Japanese Patent Application No. 3-168750 discloses a method formanufacturing polyphenylene sulfide fibers in a melt spun process.Polyphenylene sulfide is melted and spun through a spinneret whereuponthe spun yarn is cooled by blowing a cooling air flow with a temperatureof at least 45° C. onto same. The yarn is then hot drawn by passingthrough a heating zone.

Japanese Patent Application No. 9-78693 discloses polyphenylene sulfidefibers for electrical insulation, method of manufacturing the same, andelectrical insulation material. The tenacity of the melt spun and drawnfibers lies at 44 cN/tex, elongation at break lies around 20%.Polyphenylene sulfide is spun by a spinneret, the spun thread is passedthrough a high temperature atmosphere surrounded by a heating tube of 5cm to 30 cm length at a temperature between 280° C. and 350° C., afterwhich it is solidified by cooling uniformly by air at 100° C. or less,preferably 20-80° C. This undrawn yarn is fed continuously to the heatdrawing process and normally is drawn in a plurality of stages of 2stages or more, without being wound off The draw ratio should be3.0-5.5.

Japanese Patent Application No. 2-219475 discloses polyphenylene sulfidefibers and method of manufacturing same. The polyphenylene sulfidefibers consisting of a continuous filament having a tenacity of at least44 cN/tex and elongation at break of at least 20%. For the processpellets of polyphenylene sulfide fiber polymer are melted at atemperature of 310-340° C. and passed successively through a filter andspinneret holes of 0.1-0.5 mm diameter to form a spun thread strand,which is subsequently passed through a high-temperature atmosphereenclosed by a heat insulating tube or a heating tube disposed over adistance of 5-30 cm immediately below the spinneret in which saidspinneret holes are formed and controlled to an ambient temperature of150-350° C., and then cooled by a warm air flow or cool air flow at 100°C. or below.

SUMMARY

It is an object of the present invention to provide another process forthe production of polyphenylene sulfide multifilament yarns in which thecooling is further improved to yield a polyphenylene sulfidemultifilament yarn with desired properties regarding breaking tenacityand elongation at break. It is another object of the invention toprovide a polyphenylene sulfide multifilament yarn with desiredproperties regarding breaking tenacity and elongation at break.

DETAILED DESCRIPTION OF EMBODIMENTS

This object is achieved by a process for producing a polyphenylenesulfide multifilament yarn comprising the steps in which a melt ofpolyphenylene sulfide is fed to a spinning device, the melt is extrudedthrough a spinneret with a plurality of spinneret holes to form afilament bundle with a plurality of filaments, cooling the filamentbundle in a cooling zone and winding the filaments after solidifying,characterized in that only after a time period between 0.1 sec and 0.3sec after leaving the spinneret the filaments of the spun yarn aresubjected to an active cooling stage. In a preferred embodiment of theprocess the temperature of the filaments after leaving the spinneret andbefore active cooling is at least T_(spin)−150° C. preferably at leastT_(spin)−50° C. The maximum temperature of the filaments is T_(spin).T_(spin) means the spinning temperature in ° C. for the polyphenylenesulfide melt. After leaving the spinneret the spun yarn is thus notsubjected to an active cooling stage for 0.1 sec to 0.3 sec.

The process according to the invention comprises the steps in which amelt of polyphenylene sulfide is fed to a spinning device, the melt isextruded through a spinneret with a plurality of spinneret holes to forma filament bundle with a plurality of filaments, cooling the filamentbundle in a cooling zone and winding the filaments after solidifying.

The cooling behavior of polyphenylene sulfide is certainly complicatedand dependent upon a series of parameters. The cooling process alsoleads to differences in the crystallization behavior of the filaments.The cooling thus determines the crystallization of the polymers in thefilament to a large degree, which is noticeable in the later usage ofthe filaments, for example in drawing.

The viscosity of the polyphenylene sulfide polymer chips used as rawmaterial for the process according to the invention lies between 150 and300 Pas measured according to ISO/FDIS 11443 (12/2004) at a temperatureof 310° C. and a shear rate of 1200 s−¹.

The polymer used in the process according to the invention essentiallyhas a linear structure, i.e. the level of trifunctional monomers used islower than 0.1%. The polymer is of course an uncrosslinked polymer as itcould otherwise not be used in a melt spinning process. The polymerconsists of at least 90% by weight of uncrosslinked linear polyphenylenesulfide.

In the process according to the invention, the length of this stagewhere the spun yarn is not subjected to active cooling is determined bythe speed of the yarn and the time it is not subjected to activecooling. The speed of the yarn is calculated as the winding speed of thefirst godet in the process. The winding speed of the first godet, i.e.the speed the yarn is drawn off the spinneret, lies preferably in therange of 200 m/min to 1000 m/min. Thus, for example, with a windingspeed of the first godet of 300 m/min and a time period before activecooling of approx. 0.15 sec the length of the stage where the spun yarnis not subjected to active cooling is approx. 75 cm.

In a preferred embodiment of the process of the invention, drawing offthe yarn is performed at a speed in the range of 250 m/min to 500 m/min.

There is in principle no restriction on the number of individual threadsor filaments comprising a multifilament yarn. A multifilament generallycomprises between 10 and 500 filaments, and frequently between 50 and300 filaments. The multifilaments are usually collected in the course ofthe process into so-called filament bundles and are wound up in thisform. The linear density of the filaments comprising the continuousyarns, i.e. the filament linear density, can also vary within widelimits. In general, however, filament linear densities in the range ofapprox. 1 to approx. 30 dtex, and preferably between 5 and 30 dtex, morepreferably between 5 and 20 dtex, most preferably between 5 and 10 dtexare used. The filament linear density refers to the final yarn whichmight have been subjected to drawing.

Between the spinneret and the beginning of the first active cooling zonethe filament bundle may be passed through a perforated or porous tubefor a time period between 0.1 sec and 0.3 sec. While being passedthrough a perforated or porous tube the temperature of the yarn is atleast T_(spin)−150° C. preferably at least T_(spin)−50° C. Suchperforated or porous tubes are also known to those skilled in the artunder the term self suction tubes. They make it possible to pull gaseousmedium through the filament bundle in such a way that intermingling canbe mostly avoided. The filament bundle may also be led betweenperforated or porous panels. The filament bundle is led through orbetween perforated or porous tubes or panels in such a way that agaseous medium reaches the filaments by self-suction. The filamentbundle thus pulls the gaseous cooling medium in its proximity, such asthe ambient air, so that the gaseous medium flows mostly parallel to thedirection in which the filament bundle is moving.

In another preferred embodiment there is between the spinneret and thebeginning of the first active cooling zone a so-called heated tube witha temperature between T_(spin)−50° C. and T_(spin)+10° C. As describedthe yarn runs through that heated tube for a time period between 0.1 secand 0.3 sec. Depending upon the type of filament, the length of thiselement, which is known to those skilled in the art, is determined bythe speed of the yarn to be fed through it. However, the length of thiselement is at least 40 cm.

In a more preferred embodiment of the process according to the inventionthere is, between the spinneret and the beginning of the first activecooling zone, a heated tube with a temperature between T_(spin)−50° C.and T_(spin)+10° C. and subsequently a perforated or porous tube orperforated or porous panels. The yarn runs through the combination of aheated tube and a perforated or porous tube or panel for a time periodbetween 0.1 sec and 0.3 sec.

In one embodiment of the active cooling zone of the process according tothe invention a gaseous cooling medium is blown into the filamentbundle. The flow of the gaseous cooling medium is directed in such a waythat it reaches the filaments from one side or circumferentially. Thefilament bundle is thus being blown on with a gaseous cooling medium inthe cooling zone in such a way that the gaseous cooling medium flowsthrough the filament bundle transversely. The gaseous cooling medium mayalso be blown into the upper section of the cooling zone so that thereis a downward flow of cooling medium parallel to the filaments. Thetemperature of the gaseous cooling medium is preferably 20-100° C.Cooling medium is preferably air.

After passing through a perforated tube, a heated tube with atemperature between T_(spin)−50° C. and T_(spin)+10° C. or a combinationof a heated tube and a perforated tube for a time period between 0.1 secand 0.3 sec the filaments are preferably cooled in another embodiment ofthe active cooling zone by a fluid, consisting wholly or partly of acomponent that is liquid at room temperature the filaments.

The fluid used for cooling in the cooling zone consists wholly or partlyof a component that is liquid at room temperature such as water, watervapour, alcohol or mixtures of these components with gaseous media, e.g.air or nitrogen. The cooling zone can be implemented in variousembodiments in the method of the invention. In a preferred embodiment,the continuous yarns are cooled while being fed through the cooling zoneessentially by a fluid consisting partly or entirely of water.

In a simple and advantageous embodiment of the method of the invention,the continuous yarns are cooled essentially by a water-bath while beingfed through the cooling zone. Care must be taken here that the watertemperature is not too high, to avoid adhesion between the filaments.

The most preferred embodiment, however, is one in which thepolyphenylene sulfide multifilament yarn is cooled, on passing throughthe cooling zone, essentially by a spray mist of small water droplets.This embodiment exploits the fact that small water droplets, preferablywith average diameter not exceeding 150 μm, can dissipate asignificantly greater amount of heat than is possible by passage througha water-bath. The reason for this is the additional heat of vaporisationof the droplets, the necessary heat energy being extracted from theyarns. The droplets are advantageously brought into contact with thecontinuous yarns through nozzles. In this case the cooling zone can takethe form of, for example, a mist chamber with nozzles attached at itslower end, which direct the spray mist onto the yarns in the directionopposite to that of the yarn movement and at an angle of, e.g. 45°.

After spinning the filaments of the polyphenylene sulfide multifilamentyarn through a spinneret with a plurality of holes, drawing off the yarnfilaments at a speed in the range of 200 m/min to 1000 m/min, subjectingthe yarn filaments to a temperature of at least T_(spin)−150° C.preferably at least T_(spin)−50° C. for a time period between 0.1 secand 0.3 sec, cooling the filaments of the yarn, the filaments may bedried, in preparation for the drawing process, by a method known per se,e.g. by the application of air, for example compressed air at ambienttemperature, by means of a blower. Drawing of the yarn filaments in aform known per se may be carried out after the cooling. A drawing ratiofrom 3 to 6 may be achieved in a single or multiple stage drawing.

In a preferred embodiment of the process according to the inventiondrawing is carried out after cooling in a first and second drawing stepwith the yarn tension and/or temperature being constant in the firstdrawing step and with the yarn tension being increased in the secondstep. The drawing in a first and second step is preferably being carriedout on godets surrounded by ambient air. The yarn tension and/or thetemperature is being increased in the second step. In the first drawingstep a steam nozzle is preferably present. It is believed that theadvantages of drawing the yarn filaments in a first and second drawingstep with the yarn tension and/or temperature being constant in thefirst drawing step and with the yarn tension and/or temperature beingincreased in the second step may also be applied to other melt spinningprocesses.

In a more preferred embodiment of the process of the invention drawingin a first and second step is carried out in such a way that the yarntension in the second drawing step is increased from a start value to anend value by means of a plurality of draw godets, by increasing thespeed of successive draw godets. Counted from the start value of theyarn tension to the attainment of the end value, more than twoconsecutive draw godets, and especially preferably more than three and,for example, more than five godets are used. An overall amount of up to30 draw godets may be used for the process.

It has surprisingly been found that in such an embodiment the fluffindex of the filament can be considerably reduced.

In the process according to the invention, the temperature in the seconddrawing step can also be increased from a start value to an end value byheating consecutive draw godets to successively higher temperatures thatincrease from a start value to an end value, it being immaterial for theabove-mentioned lowering of the fluff index whether two or more than twoconsecutive draw godets, counted from the start value of the temperatureto the end value, are used.

In a most preferred embodiment drawing in the second drawing step iscarried out in such a way that the yarn tension is increased from astart value to an end value by means of a plurality of draw godets, byincreasing the speed of successive draw godets and the temperature isincreased from a start value to an end value by heating consecutive drawgodets to successively higher temperatures that increase from a startvalue to an end value.

Drawing can optionally be followed by a relaxation step on one or morerelax godets.

After drawing in a first and second drawing step winding up of the yarnis carried out at a speed in the range of 1000 m/min to 4000 m/min.

The invention also pertains polyphenylene sulfide multifilament yarnsobtainable by a process according to the invention. Said polyphenylenesulfide multifilament yarns exhibit a breaking tenacity of at least 50cN/tex, preferably 55 cN/tex. In another preferred embodiment thebreaking tenacity of the polyphenylene sulfide multifilament yarn is atleast 60 cN/tex. In a more preferred embodiment the breaking tenacity ofthe PPS filament yarn is at least 65 cN/tex. In a most preferredembodiment the breaking tenacity of the PPS filament yarn is at least 70cN/tex. The breaking tenacity of the polyphenylene sulfide multifilamentyarns obtainable by a process according to the invention should notexceed 80 cN/tex.

Elongation at break of the polyphenylene sulfide multifilament yarnobtainable by a process according to the invention lies between 8% and16% for yarns exhibiting a breaking tenacity of 60 cN/tex to 80 cN/tex,preferably between 10.5% and 12.5%. For polyphenylene sulfidemultifilament yarns obtainable by a process according to the inventionwith a breaking tenacity between 50 cN/tex and 60 cN/tex, elongation atbreak is preferably in the range of 16% to 30%.

The invention further pertains polyphenylene sulfide multifilamentyarns. The linear density of the filaments comprising the continuousyarns, i.e. the filament linear density, can also vary within widelimits. In general, however, filament linear densities in the range ofapprox. 5 to 30 dtex, preferably 5 to 20 dtex, most preferably 5 to 10dtex are used.

The polyphenylene sulfide polymer used for the multifilament yarnaccording to the invention essentially has a linear structure, i.e. thelevel of trifunctional monomers used is lower than 0.1%. The polymer isof course an uncrosslinked polymer as it could otherwise not be moltenand used in a melt spinning process. The polymer consists of at least90% by weight of uncrosslinked linear polyphenylene sulfide. Thepreferred polyphenylene sulfide (PPS) generally contains at least 50 mol% and in particular at least 70 mol % of phenylene sulfide units, and isknown, for example, under the name of Fortron®.

The polyphenylene sulfide multifilament yarns exhibit a breakingtenacity of at least 50 cN/tex, preferably 55 cN/tex. In anotherpreferred embodiment the breaking tenacity of the polyphenylene sulfidemultifilament yarn is at least 60 cN/tex. In a more preferred embodimentthe breaking tenacity of the PPS filament yarn is at least 65 cN/tex. Ina most preferred embodiment the breaking tenacity of the PPS filamentyarn is at least 70 cN/tex. The breaking tenacity of the polyphenylenesulfide multifilament yarns according to the invention usually does notexceed 80 cN/tex.

The polyphenylene sulfide multifilament yarn according to the inventionexhibits a filament linear density of 5 dtex to 30 dtex, an overalllinear density of 500 dtex to 2500 dtex, a breaking tenacity in therange of 50 cN/tex to 80 cN/tex and an elongation at break of 8% to 16%for a yarn with a breaking tenacity in the range of 60 cN/tex to 80cN/tex and an elongation at break of 16% to 30% for a yarn with abreaking tenacity in the range of 50 cN/tex to 60 cN/tex

As a result of the high elongation at break of 8% to 16% for a yarn witha breaking tenacity in the range of 60 cN/tex to 80 cN/tex and anelongation at break of 16% to 30% for a yarn with a breaking tenacity inthe range of 50 cN/tex to 60 cN/tex, the polyphenylene sulfidemultifilament yarn according to the invention has a high energyabsorption capacity, which, combined with a filament linear density of 5dtex to 30 dtex, an overall linear density of 500 dtex to 2500 dtexopens up attractive possibilities for use as described below, in fieldsof application where such a combination of properties is important.

In another preferred embodiment of the polyphenylene sulfidemultifilament yarn according to the invention, the yarn has, for a spunlength of 10 000 m, a fluff index of less than 2500, and preferably lessthan 1000, more preferably less than 500.

In yet another preferred embodiment of the polyphenylene sulfidemultifilament yarn according to the invention the filaments of the yarnhave a linear density of 5 dtex to 20 dtex.

The breaking tenacity of the polyphenylene sulfide multifilament yarnaccording to the invention lies preferably in the range of 50 cN/tex to60 cN/tex.

The polyphenylene sulfide multifilament yarn according to the inventionmay be obtained by the process for producing a polyphenylene sulfidemultifilament yarn according to the invention

The advantageous combination of properties in the polyphenylene sulfidemultifilament yarn according to the invention and in the polyphenylenesulfide multifilament yarn resulting from a process according to theinvention makes the use of this multifilament attractive in applicationfields where high values of filament and overall linear density,breaking tenacity, and elongation at break, coupled with high thermaland chemical stability, are important, as for example for production ofneedle bonded fabrics, backing fabrics, particularly for use in filtermedia, for aircraft interior fittings, or as hose reinforcement.

If the polyphenylene sulfide multifilament yarns obtainable by a processaccording to the invention or the polyphenylene sulfide multifilamentyarns according to the invention are used for filter media or needlebonded fabrics a linear density from 900 dtex to 1400 dtex is preferred.In a more preferred embodiment the polyphenylene sulfide multifilamentyarn has a linear density from 1000 dtex to 1200 dtex.

For the purposes of the present invention, the filament linear density,breaking tenacity and elongation at break is determined in accordancewith ASTM D805. These parameters have to be determined as mean value ofat least 5 individual measurements. The fluff index is determined withthe FRAYTEC5 from Enka Tecnica.

The present invention is described in more detail in the followingnon-limiting examples.

EXAMPLES Example 1

Linear polyphenylene sulfide (Fortron®0320C0) is molten and fed to aspinneret with 200 holes. The holes are circular and have a diameter of300 μm. The spun multifilament is drawn off at a speed of 300 m/min,passed through a heated tube of app. 12 cm length with a temperature inthe heated tube of 300° C. to 320° C. and a perforated tube of app. 100cm length, passed then through an active cooling zone in which thefilaments are cooled by a spray mist of small water droplets, drawn infirst and second drawing steps, and subsequently the yarn tension isrelaxed by 0.7% in a relaxation step before the multifilament is woundup at a speed of 1350 m/min.

In the first drawing step, drawing is performed with a draw ratio of4.02. Draw godets 1-4 are used for this purpose, godet 1 having atemperature of 70° C., godets 2 and 3 being unheated, and godet 4 havinga temperature of 125° C.

In the second drawing step, drawing is performed with a draw ratio of1.12 so that the total draw ratio amounts to 4.50. Draw godets 5-20 areused for this purpose, their temperatures and speeds being shown inTable 1. Table 1 shows that in the second drawing zone the filamenttension is increased from its start value at godet 5 to its end value atgodet 10 by means of six consecutive godets.

TABLE 1 Speed Temperature Draw godet (n) [m/min] [° C.] 5 1205 125 61234 125 7 1263 170 8 1292 200 9 1321 240 10-13 1350 240 14-20 1350 240

Example 2

Example 2 was carried out in the same way as Example 1, except that inthe second drawing zone the yarn tension and temperature were increasedas shown in Table 2. Table 2 shows that in the second drawing zone theyarn tension is increased from its start value at godet 6 to its endvalue at godet 7 by means of two consecutive godets.

TABLE 2 Speed Temperature Draw godet (n) [m/min] [° C.] 5 1205 125 61205 125 7 1350 170 8 1350 200 9 1350 240 10-13 1350 240 14-20 1350 240

Example 3

Example 3 was carried out in the same way as Example 1, except that inthe second drawing zone the yarn tension and temperature were increasedas shown in Table 3. Table 3 shows that in the second drawing zone theyarn tension is increased from its start value at godet 6 to its endvalue at godet 7 by means of two consecutive godets.

TABLE 3 Speed Temperature Draw godet (n) [m/min] [° C.] 5 1205 125 61205 125 7 1350 240 8 1350 240 9 1350 240 10-13 1350 240 14-20 1350 240

Example 4

Example 4 was carried out in the same way as Example 1, except that inthe second drawing zone the yarn tension and temperature were increasedas shown in Table 4. Table 4 shows that in the second drawing zone theyarn tension is increased from its start value at godet 5 to its endvalue at godet 10 by means of six consecutive godets.

TABLE 4 Speed Temperature Draw godet (n) [m/min] [° C.] 5 1205 125 61234 125 7 1263 240 8 1292 240 9 1321 240 10-13 1350 240 14-20 1350 240

Example 5

Table 5 shows the properties of the polyphenylene sulfide multifilamentyarn resulting from Examples 1 to 4. Table 5 shows that the embodimentsof the process according to the invention in Examples 1 to 4 result in apolyphenylene sulfide multifilament yarn according to the inventionhaving a filament linear density of 5 dtex to 30 dtex, an overall lineardensity of 500 dtex to 2500 dtex, a breaking tenacity in the range of 50cN/tex to 80 cN/tex and an elongation at break of 16% to 30% for a yarnwith a breaking tenacity in the range of 50 cN/tex to 60 cN/tex.Comparison of Examples 1 and 4 with Examples 2 and 3 indicates that ifthe yarn tension is increased in the second drawing zone from its startvalue at godet 5 to its end value at godet 10 by means of sixconsecutive godets, a considerably lower fluff index results than if theyarn tension is increased in the second drawing zone from its startvalue at godet 6 to its end value at godet 7 by means of two consecutivegodets.

TABLE 5 Example 1 Example 2 Example 3 Example 4 Filament linear density5.39 5.24 5.32 5.32 [dtex] Overall linear density 1077 1047 1063 1063[dtex] Breaking tenacity 57.7 54.5 57.1 57.2 [cN/tex] Elongation atbreak [%] 17.5 18.0 17.9 17.3 Hot-air shrinkage [%] 12.3 11.1 11.1 12.2Elongation for load of 11.9 13.5 12.6 11.8 45 N [%] Modulus at 0.5-2%447 412 433 461 elongation [cN/tex] Fluff index [10000 m⁻¹] 409 20001818 291

1. A polyphenylene sulfide multifilament yarn obtained from a process comprising: feeding a melt of polyphenylene sulfide to a spinning device; extruding the melt through a spinneret with a plurality of spinneret holes to form a filament bundle with a plurality of filaments; subjecting the filament bundle to a passive cooling stage, which includes passing the filament bundle through a perforated or porous tube or passing the filament bundle between perforated or porous panels for a time period of between 0.1 s to 0.3 s after the filament bundle leaves the spinneret; subjecting the filament bundle to an active cooling stage; drawing the filament bundle after subjecting the filament bundle to the passive cooling stage and the active cooling stage; and winding the filaments after solidifying and the drawing.
 2. A polyphenylene sulfide multifilament yarn having a filament linear density of 5 dtex to 30 dtex, an overall linear density of 500 dtex to 2500 dtex, a breaking tenacity in the range of 50 cN/tex to 80 cN/tex, wherein a yarn with a breaking tenacity in the range of 60 cN/tex to 80 cN/tex exhibits an elongation at break of 8% to 16% and a yarn with a breaking tenacity in the range of 50 cN/tex to 60 cN/tex exhibits an elongation at break of 16% to 30%.
 3. The polyphenylene sulfide multifilament yarn according to claim 1, wherein the polyphenylene sulfide consists of at least 90% by weight of an uncrosslinked linear polyphenylene sulfide polymer material.
 4. The polyphenylene sulfide multifilament yarn according to claim 2, wherein for a spun length of 10,000 m the multifilament yarn has a fluff index of less than
 2500. 5. The polyphenylene sulfide multifilament yarn according to claim 2, wherein for a spun length of 10,000 m the multifilament yarn has a fluff index of less than
 1000. 6. The polyphenylene sulfide multifilament yarn according to claim 2, wherein for a spun length of 10,000 m the multifilament yarn has a fluff index of less than
 500. 7. The polyphenylene sulfide multifilament yarn according to claim 2, wherein the multifilament yarn has a filament linear density of 5 dtex to 20 dtex.
 8. The polyphenylene sulfide multifilament yarn according to claim 2, wherein the multifilament yarn has a breaking tenacity in the range of 50 cN/tex to 60 cN/tex.
 9. Backing fabrics comprising the polyphenylene sulfide multifilament yarn according to claim
 1. 10. Backing fabrics comprising the polyphenylene sulfide multifilament yarn according to claim
 2. 